According to many opponents of Office Open XML the lack of interoperability between Microsoft documents formats and the new ODF format is all because Microsoft did not cooperate with the OASIS TC when they were developing ODF.
Stangly enough it seems that Gary Edwards who actually was a member of the OASIS TC developing ODF has a totally different view on why ODF has no feature for being compatible with Micrsoft Office documents.:
"For the near five years that i have been a member of the OASIS ODF TC, Sun has opposed any and all efforts to improve interoperability with Microsoft applications, documents, and bound workgroup-workflow business processes.
This goes all the way back to the very first TC meeting on December 14th, 2002, when the enterprise publication, content and archive management systems contingent of the OASIS TC wanted the "proposed" ODF charter amended to include as one of the primary objectives, "compatibility with existing file formats and interoperability with existing applications".
And yes, that proposed charter change specifically included compatibility and interoperability with Microsoft applications, documents and processes!!
Sun opposed that change and has consistently opposed all interoperability enhancements since."
But luckily it is still all Microsofts fault, at least according to Gary:
"Someone needs to go back to that 2004 agreement between Microsoft and Sun. You know, the one that saved Sun the company! There is clear evidence, stretching throughout the years of ODF discussions, that Sun has traded ODF universal interoperability for a sweet sweet hardware deal with Microsoft. Overwhelming evidence."
Which is a bit strange because he also claims that Sun blocking interoperability with MS office document started from the day the charter was made in 2002 when Sun and Microsoft were still bitter rivals in court.
So what about ODF interoperability with ODF now:
"There are three characteristics Sun has steadfastly opposed. And now we finally have an explanation other than that the StarOffice Hamburg group was terminally "stuck in 1995".
These characteristics are important because the world is not a clean slate. Microsoft Office controls over 95% of the existing documents, applications and bound workgroup-workflow business processes.
Without these three bridge characteristics, ODf becomes impossible to implement given where the world today finds itself – 95% bound to MSOffice:
... Compatibility with existing file formats – including MS binary documents
... Interoperability with existing applications – including MSOffice applications
... Convergence :: the application-platform-vendor independent portable file format ability to fluidly and transparently transition desktop-server-device-web information systems.
Sun's opposition to and failure to support the interoperability enhancements to ODf that would have addressed these concerns is a matter of public record"
A sound of bitter disappointment in the lack of interoperability in ODF but also and especially disappointment in Sun being responsible for it
"But what about those of us who really believed that ODf could become that elusive universal file format, and spent years trying?"
And reffering to Sun:
"They sold us out!"